The present invention relates to a recording material, and more particularly, to a recording material which is especially suitable for use in the ink-jet recording system.
The recent spread of personal computers not only in enterprises, but also at home has brought about an increase in the printing of information by printers. The recent improvement in performance of personal computers has made it possible to handle image data consisting of a large amount of information very easily and has brought about an increase in the printing of images in full color.
Examples of printing and recording systems by printers include ink-jet recording systems, heat-transfer recording systems, sublimation transfer recording systems and direct heat-sensitive recording systems. All of these systems require a recording material to have characteristics including a high printing density, an excellent color developing property, resistance to blotting during printing, and resistance to ink flow and blotting when the recording material is wetted with water.
For the ink-jet recording systems in which recording is made by spraying fine ink droplets onto a recording material such as paper, it is particularly important to ensure that the ink does not blot the recording material when adhering to it, nor should the ink on the recording material flow or blot with water contact.
Attempts have been made to add various compounds to a recording material to meet the requirements stated above. For example, studies into the addition of various chemicals into a recording material have been made. Such chemicals include polyethyleneimine, a quaternary compound of polyvinyl pyridine disclosed in Japanese Laid-Open Patent Application (JP-A) No. 56-84992, a condensation product of polyalkylenepolyaminedicyandiamide disclosed in Japanese Laid-Open Patent Application (JP-A) No. 60-49990, and a reaction product of a secondary amine and epihalohydrin disclosed in Japanese Laid-Open Patent Application (JP-A) No. 6-92012.
However, a recording material that meets all of the above-stated requirements for the various printing and recording systems is not yet known. Since the ink-jet recording system normally employs the ink containing a water-soluble dye or water-dispersible dye, it is especially difficult to solve the problems of ink blotting during printing, and flowing or blotting of ink on the recording material with water contact after printing, even if a recording material containing the above-mentioned chemicals is used.
In view of these technical problems, it is an object of the present invention to provide a recording material, which is particularly suitable for use in an ink-jet recording system, which does not exhibit blotting of ink during printing and flowing or blotting of ink with water contact after printing.
The inventors have made detailed studies into means for achieving the above-mentioned object and, as a result, have found that the addition of a polyguanidine salt into a substrate makes it possible to obtain a recording material which does not exhibit blotting of ink during printing and flowing or blotting of ink with water contact after printing. The inventors have also found that a recording material comprising a substrate and a polyguanidine salt contained in the substrate is particularly effective in preventing blotting of ink during printing, and flowing or blotting of ink by water contact after printing, when inks for the ink-jet recording system which contain a water-soluble dye or a water-dispersible dye are used, thereby accomplishing the present invention.
Thus, the present invention provides a recording material comprising a substrate and a polyguanidine salt of the general formula (1) contained in the substrate: 
wherein R1 and R2 may be the same or different, and each represents a group selected from the group consisting of a divalent aliphatic hydrocarbon group, a divalent aromatic hydrocarbon group and a divalent alicyclic hydrocarbon group; HX is an acid selected from the group consisting of a mineral acid and an organic acid; and p is an integer of 1 to 250.
According to the present invention, the polyguanidine salt is preferably a polyguanidine salt of the general formula (2): 
wherein HX is an acid selected from the group consisting of a mineral acid and an organic acid; n is an integer of 3 to 500; and m is an integer of 2 to 6.
The present invention also provides a recording material in which the substrate comprises at least one material selected from the group consisting of paper, a fibrous material and a resin film.
The substrate of the recording material of the present invention preferably contains the polyguanidine salt in an amount of 0.01 to 10 g per square meter in the vicinity of its surface. And the recording material preferably contains the polyguanidine salt in an amount of 0.01 to 10% by weight based on a total weight of the recording material.
The present invention further provides a recording material which is suitable for an ink-jet recording system.
The present invention will now be described in detail.
The recording material of the present invention comprises a substrate and a polyguanidine salt of the general formula (1) contained in the substrate: 
wherein R1 and R2 may be the same or different, and each represents a group selected from the group consisting of a divalent aliphatic hydrocarbon group, a divalent aromatic hydrocarbon group and a divalent alicyclic hydrocarbon group; HX is an acid selected from the group consisting of a mineral acid and an organic acid; and p is an integer of 1 to 250.
Here, the polyguanidine salt means a salt formed from a polyguanidine of the general formula (3) and an acid HX: 
wherein R1 and R2 may be the same or different, and each represents a group selected from the group consisting of a divalent aliphatic hydrocarbon group, a divalent aromatic hydrocarbon group and a divalent alicyclic hydrocarbon group; and p is an integer of 1 to 250.
HX in the general formula (1) is not particularly limited as long as it is an acid that forms a salt with guanidine. Any of various known mineral or organic acids is preferably used. The mineral acids that can be used include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and carbonic acid. The organic acids that can be used include monobasic acids represented by acetic acid, lactic acid and gluconic acid; and polybasic acids represented by maleic acid, fumaric acid and tartaric acid. In the present invention, phosphoric acid, hydrochloric acid and lactic acid are preferably used.
The polyguanidine salt of the general formula (1) can be obtained by, for example, reacting diamine with diisothiocyanate to obtain polythiourea, converting xe2x95x90S in the thiourea group in the polythiourea into xe2x95x90NH by an adequate functional group conversion to obtain polyguanidine of the general formula (3), and neutralizing the polyguanidine with an acid HX. Since the polyguanidine salt of the general formula (1) can be obtained by polyaddition as described above, the terminal of its molecule may form amino group (xe2x80x94NH2) derived from diamine, isothiocyanate group (xe2x80x94NCS) derived from diisothiocyanate, or a functional group derived by the above-mentioned functional group conversion and/or neutralization.
In general formula (1), p is an integer of 1 to 250. Preferably, p is an integer of 3 to 250. When p exceeds 250, the polyguanidine salt has too high molecular weight for easy handling. R1 and R2 are preferably a divalent aliphatic hydrocarbon group, and more preferably a divalent aliphatic hydrocarbon group having 1 to 12 carbons. In this case, R1 can be different from R2. In the present invention, the polyguanidine salt may be used alone or in combination of two or more kinds.
In present invention, the polyguanidine salt of the general formula (1) is preferably a polyguanidine salt of the general formula (2): 
wherein HX is an acid selected from the group consisting of a mineral acid and an organic acid; n is an integer of 3 to 500, and m is an integer of 2 to 6.
The general formula (1) wherein R1 and R2 are both xe2x80x94(CH2)mxe2x80x94 corresponds to the general formula (2). The polyguanidine salt of the general formula (2) can be obtained by, for example, reacting diamine having a chemical structure of H2Nxe2x80x94(CH2)mxe2x80x94NH2 with disothiocyanate having a chemical structure of SCNxe2x80x94(CH2)mxe2x80x94NCS to obtain polythiourea, converting xe2x95x90S in the polythiourea into xe2x95x90NH, and then neutralizing the resultant product with an acid HX. The polyguanidine salt of the general formula (2) has a portion of alkylene, therefore it may be called a polyalkyleneguanidine salt. The acid HX in the general formula (2) is the same as those described above.
In the general formula (2), n is preferably 3 to 500 and more preferably 6 to 500. When n is less than 3, resistance to blotting of ink and flowing of ink with water contact tends to be deteriorated. When n exceeds 500, there is a tendency that the molecular weight of the polyguanidine salt becomes too high for easy processing.
The polyguanidine salt described above is added into the substrate in the present invention. The substrate may be paper, a fibrous material, or a resin film.
Here, the paper used as the substrate includes paper made from pulp; paper made from mixture of pulp and synthetic fibers based on polyester, nylon or acrylic; and a synthetic paper having a micro-porous polymer layer on a base film such as polyester film, polypropylene film, polystyrene film and polyvinyl chloride film. All of above paper are suitably used for the recording material for the ink-jet printing system.
The fibrous material used as the substrate includes a woven fabric, a knitted fabric, and a nonwoven fabric made from synthetic fibers, natural fibers, semi-synthetic fibers, or hybrid fibers based on natural and synthetic fibers. A nonwoven fabric made from a thermoplastic resin can be used, too.
The resin film used as the substrate includes polyester film, polyvinyl chloride film, and polyolefin film. Surface treatment can be given to these films as required.
The recording material of the present invention can be manufactured according to any known processes without particular limitation.
For example, when paper made from pulp or paper made from mixture of pulp and synthetic fibers is employed as the substrate for the recording material, the recording material can be manufactured by performing papermaking process of pulp or mixture of pulp and synthetic fibers in the presence of the polyguanidine salt of the general formula (1) or its solution. Alternatively, after paper is manufactured, the polyguanidine salt of the general formula (1) can be coated or sprayed on the paper.
When a synthetic paper, a fibrous material or a resin film is employed as the substrate for the recording material, the recording material can be manufactured by coating, padding or spraying the polyguanidine salt of the general formula (1) on the substrate.
The amount of the polyguanidine salt in the recording material is not particularly limited, and can be selected according to the purpose of its application. For example, the recording material preferably contains the salt in an amount of 0.01 to 10 g per square meter. In this case, the recording material preferably contains the polyguanidine salt in the vicinity of its surface. Here, the vicinity of the surface means a region including the outermost surface of the recording material. When the amount of the polyguanidine salt is less than 0.01 g per square meter, resistance to blotting of ink and flowing of ink with water contact tends to be deteriorated. When the amount exceeds 10 g per square meter, there is a tendency that the hand-touch of the recording material is changed comparing with that of the recording material containing no polyguanidine salt.
Alternatively, the recording material preferably contains the polyguanidine salt in an amount of 0.01 to 10% by weight based on its total weight. In this case, the polyguanidine salt may be uniformly distributed throughout the recording material, or may be unevenly distributed in the recording material. When the amount of the polyguanidine salt is less than 0.01% by weight, resistance to blotting of ink and flowing of ink with water contact tends to be deteriorated. When the amount exceeds 10% by weight, there is a tendency that the hand-touch of the recording material is changed comparing with that of the recording material containing no polyguanidine salt.
The recording material of the present invention may further contain other additives as required. For example, it may contain a binder, an inorganic pigment or an organic pigment which have usually been employed in this type of application. Examples of the binder include oxidized starch and polyvinyl alcohol. Examples of the inorganic pigment include soft calcium carbonate, heavy calcium carbonate, kaolin (china clay), talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfate, zinc carbonate, aluminum silicate, diatomaceous earth, calcium silicate, synthetic silica, aluminum hydroxide and alumina. Examples of the organic pigment include a styrene plastic pigment, an acrylic plastic pigment, a micro-capsulated pigment and a carbon resin pigment.
As explained above, in the present invention, the recording material does not exhibit blotting of ink during printing, and flowing or blotting of ink with water contact after printing because the recording material contains the polyguanidine salt of the general formula (1). This performance can be obtained for various printing systems. Although the mechanism for the resistance to blotting and flowing of ink is not fully understood, the inventors presume that the polyguanidine salt possibly exert a strong interaction with inks used in various printing systems, or with dyes and pigments contained therein. The inventors also presume that the interaction may be due to the chemical structure of the polyguanidine salt, which has a guanidine portion and a hydrophobic portion (aliphatic, aromatic or alicyclic hydrocarbon group) alternately.
The ink widely used for the ink-jet printing system is made by dissolving a water-soluble dye such as an acid dye, a basic dye and a direct dye into a solvent such as water, alcohol and glycol. The ink containing an oil-soluble dye or pigment is also applicable to the ink-jet recording system. In the present invention, the polyguanidine salt in the recording material is believed to have an ability to hold the ink tightly in the place where the ink is applied by printing. Therefore, the recording material of the present invention is particularly suitable for use in the ink-jet recording system.